Making a simple heart-based health meter

Easier said than done, by following [ tutorial video][1] I’ve been able to add finally a visual heart display to my game HUD but only the visual part.

340221-heart-display.png

Unfortunately, once the tutorial reaches the how-to of implementing the actual functionality of the health meter is where I get stuck, as the tutorial’s implementation involves percentage-based material that isn’t of interest to me and only serves to make things extremely complicated.

All I want is a relatively simple, upgradeable heart-based health system based on rudimentary addition/subtraction but as it stands right now, is all I currently have:

Game HUD Event Graph:

‘Add Heart’ Function:

Does anyone know how I can add the rest of the actual functionality to my health meter?